In the United States, two solar photovoltaic (PV) array configurations, grounded and ungrounded, are permitted by the National Electric Code (NEC), Section 690. The maximum voltage of a PV array is currently limited to 600 Vdc with respect to earth in grounded systems and 600 Vdc in ungrounded systems because of PV module insulation limitations. The NEC also requires that PV systems installed on dwellings have a means of detecting and interrupting fault currents from the PV array to earth ground. These faults are commonly caused by water intrusion into wiring junction boxes, degradation of the array wiring insulation, or a failure in the solar module insulating materials. Such faults can cause a low energy leakage path or a destructive direct current arc. The intent of the code, with respect to ground faults, is fire protection, not personnel protection.